Temperature-Adjusted Respiratory Rate for the Prediction of Childhood Pneumonia.

OBJECTIVES: As both fever and pneumonia can be associated with tachypnea, we investigated the relationship between body temperature and respiratory rate (RR) in young children and whether temperature-adjusted RR enhances the prediction of pneumonia.

METHODS: In this retrospective cross-sectional analysis of 91,429 children < 5 years of age presenting to an urban pediatric emergency department, the relationship between triage RR and temperature was analyzed using regression analysis. We assessed the predictive value of temperature-adjusted RR for the diagnosis of pneumonia; diagnostic performance was evaluated for continuous RR as well as World Health Organization (WHO) age-based RR thresholds.

RESULTS: The mean RR increased 2.6 breaths/minute for each 1°C increase in temperature. Interpatient variability was comparatively large; at any temperature, the interquartile range (75th percentile minus 25th percentile) varied from 4 to 16 breaths/minute. For predicting pneumonia, temperature- and age-adjusted RR was superior to age-adjusted RR: area under the curve (AUC) = 0.76 (95% confidence interval [CI], 0.75-0.78) versus AUC = 0.73 (95% CI, 0.72-0.75), respectively. Using WHO RR criteria, temperature-adjusted RR improved diagnostic discrimination, as the AUC increased from 0.58 (95% CI, 0.57-0.59) to 0.72 (95% CI, 0.70-0.73).

CONCLUSIONS: The effects of temperature on respiratory rate are modest, with a mean increase of 2.6 breaths/minute for each 1°C rise in temperature. Despite considerable interpatient variability in respiratory rates by temperature, temperature adjustment improves the diagnostic value of respiratory rate for pneumonia.